MENSTRUAL STATUS AND VALIDATION OF BODY-FAT PREDICTION IN ATHLETES

Frisch and colleagues and others have used the Mellits and Cheek method to estimate body fatness in women athletes, and a value (22%) obtained from this calculation has been interpreted as a critical fatness for the maintenance and restoration of regular menstrual cycles. In comparison with hydrostatic weighing, the Mellits and Cheek method was shown to be inaccurate in predicting either mean or individual percent body fat in women runners and body builders. No fatness threshold for the maintenance of regular menses was found. There was no difference in mean body fat between eumenorrheic (n = 19) and amenorrheic (n = 13) athletes, all of whom were less than 22% body fat. The hypothesis proposed by Frisch and colleagues (Frisch et al. 1973; Frisch and McArthur, 1974; Frisch, 1976) stating that a critical amount of body fat is necessary for the onset (17%) and maintenance (22%) of regular menstrual function persists in the literature (Frisch et al. 1980; Sanborn et al. 1982). This hypothesis is supported physiologically by the observations that adipose tissue is a conversion site of androgens to estrogens (Nimrod and Ryan, 1975; Perel and Killinger, 1979). An alteration in steroid metabolism may affect steroid feedback to the hypothalamus or pituitary gland. However, there is no evidence directly linking body composition to steroid metabolism. On the other hand, several statistical arguments (Billewicz et al. 1976; Trussell, 1978; 1980; Reeves, 1979) have been presented suggesting that the procedures used to define "critical fat" levels are highly inaccurate. Katch and Katch (1980) stated that cross-validation studies were necessary to precisely examine the degree of accuracy with which body fat can be estimated from the total body water prediction equation of Mellits and Cheek (1970). The proposed critical fatness criteria were derived from the indirect estimation of body fat from predicted total body water. Specifically, a regression equation (Mellits and Cheek, 1970) employing height and Presently at the Department of Reproductive Medicine, University of California, San Diego: La Jolla, CA 92093. institute of Environmental Stress; University of California, Santa Barbara; Santa Barba-